The present invention relates to a reflector for use in a reflective liquid crystal display device which displays an image by reflecting external light when used in OA equipment, a personal computer, a mobile phone, a mobile data terminal, or the like, to a method of fabricating the same, to the reflective display device, and a method of fabricating the same.
As AV equipment and data equipment has been scaled down to have a reduced thickness in recent years, there has been growing demand for a liquid crystal display device as a light-receiving display device. For the data equipment, a liquid crystal display device that can be mounted on a notebook personal computer with higher portability has been in increasing demand with the advent of a multimedia society. In the field of mobile data terminals, a liquid crystal display device which is lower in profile, weight, and power consumption has been required.
Such liquid crystal display devices are subdivided into a transmissive type having a backlight disposed on the rear surface of a liquid crystal panel and a reflective type having a reflector disposed therein and using external light as illuminating light. There is also a semitransmissive type comprising a half mirror, which uses ex al light reflected by a reflector as illuminating light in a bright environment, while using a backlight in combination in a dark environment. Since a reflective liquid crystal display device and a semitransmissive liquid crystal display device use a mode of displaying an image by reflecting external light and normally do not need a light source such as a backlight unit, they can be reduced particularly in power consumption, profile, and weight compared with a conventional transmissive liquid crystal display device. In a typical reflective liquid crystal display device, a scattering reflector made of aluminum or silver is disposed behind a liquid crystal panel. In a monochrome display device used in a wrist watch, a scattering reflector with a sheet polarizer is bonded to the outside of glass. As a display mode of the reflective liquid crystal display device, a TN (Twisted Nematic) mode, a STN (Super Twisted Nematic) mode, a GH (Guest-Host) mode involving the use of a dichroic dye have been used predominantly.
To achieve brighter and more satisfactory display in the reflective liquid crystal display device, it is required to reflect and scatter incident light in the normal viewing angle direction which is perpendicular to a display screen and thereby increase the intensity of the light. In addition to reflecting and scattering, in the normal viewing angle direction, external light incident at a specified angle from a specified direction, it is also desirable to similarly reflect and scatter, in the normal viewing angle direction, external light incident at arbitrary angles from different directions. As a result, it becomes necessary to fabricate a reflector having optimum reflecting properties which allow external light incident from an arbitrary direction to be used efficiently as display light. The optimum reflecting properties used here indicate the properties of the reflector with which incident light is reflected in a wide range and with a high reflectance.
In the case of using a conventional reflector such as one having a specular metal film formed on a substrate, incident light is reflected only in the direction of regular reflection so that the reflectance is low in a direction other than the regular reflection direction. This causes the problem that a screen displayed is extremely dark in a direction of visual recognition of a viewer, such as the normal viewing angle direction, which significantly degrades the display quality.
To solve the problem, a reflective liquid crystal display panel comprising a scattering reflector having a rough configuration is disclosed in, e.g., Japanese Unexamined Patent Publication No. HEI 4-243226. The scattering reflector disclosed in the publication is fabricated in accordance with the following method such that a reflecting surface thereof has a uniform configuration and is formed with high reproducibility. That is, as shown in FIG. 33A, a resist film 202 is coated on a glass substrate 201. Then, as shown in FIG. 33B, the resist film 202 is covered with a photomask 203 patterned into a specified configuration and exposed to light. Subsequently, the exposed resist film 202 is developed with a developing solution, whereby numerous projecting portions 204 as shown in FIG. 33C are formed. Since the projecting portions 204 have generally right-angled edges in cross section, the edges of the projecting portions 204 should be rounded off. By performing a heat treatment, therefore, a configuration as shown in FIG. 33D is obtained. Further, Ag is vapor-deposited over the glass substrate 201 formed with the projecting portions 204 to form a metal reflective film 206 (FIG. 33E). By the foregoing process, the scattering reflector has been fabricated.
To solve the foregoing problem, a pixel electrode having reflecting properties with which reflection of incident light in the region of regular reflection is reduced is also disclosed in, e.g., Japanese Unexamined Patent Publication No. HEI 6-27481. According to the publication, a reflector 210 comprises: a substrate 211 formed with a plurality of projecting portions 212a and 212b; a polymer resin film 214 provided over the substrate 211; and a pixel electrode 215 disposed on the polymer resin film 214, as shown in FIG. 34. The surface of the pixel electrode 215 has a continuously undulating configuration.
To form the reflector 210, the following method has been used (FIGS. 35). First, as shown in FIG. 35A, a resist film 212 made of a photosensitive resin is coated on the substrate 211 by spin coating and pre-baked at a specified processing temperature. Subsequently, the resist film 212 is exposed to light by using a photomask 213 positioned thereabove, as shown in FIG. 35B. Then, development is performed by using a developing solution to form the projecting portions 212a and 212b having different heights on the substrate 211, as shown in FIG. 35C. Subsequently, a heat treatment is performed by heating the projecting portions 212a and 212b for one hour at a specified temperature, as shown in FIG. 35D. The heat treatment rounds off the respective angular edge portions of the projecting portions 212a and 212b to form projecting portions 212a and 212b with rounded edge portions. Then, as shown in FIG. 35E, a polymer resin is spin-coated on the substrate 211 after the heat treatment to form the polymer resin film 214. Finally, the pixel electrode 215 is formed by sputtering on the polymer resin film 214 (FIG. 35F).
On the other hand, Japanese Unexamined Patent Publication No. HEI 9-292504 disclosed that, if the angle formed between an extremely small surface at the surface of a pixel electrode having a projecting and depressed configuration and a substrate surface is defined as a slope angle, the reflecting properties of a reflector, i.e., the reflectance and brightness thereof in a direction normal to a substrate, are determined by the slope angle distribution.
However, since the conventional reflector has formed the projecting and depressed configuration by forming the projecting portions by using the photoresist and melting and rounding the projecting portions with the application of heat, the configuration is determined by the roundness of the projecting portions shaped naturally by the heat-melting process so that it is difficult to precisely control the configuration. It is therefore evident that the slope angle distribution of the projecting portions has not been produced actually such that specified reflecting properties are provided. As a result, the light reflected by the conventional reflector in the regular reflection direction is increased so that brightness in the viewing angle direction is insufficient and a satisfactory paper-white property is not provided in a wide range. The conventional reflector also has the problem of seemingly metallic display because of its large dependence on an exit angle. Moreover, since the projecting portions are formed by photolithography, an extra step is added to a normal fabrication process, which causes the problem of a larger number of process steps.
To provide a uniform cell gap, a liquid crystal display device comprises spacers each having a given size or height between a pair of substrates. Specifically, it is common to use not only ball-shaped (spherical) spacers in the cell of a display element but also ball-shaped or fiber-like spacers which are blended in a seal resin coated into a frame-like configuration on the periphery of the substrate. If the spacers are scattered on the substrate of the conventional reflective liquid crystal display device comprising the scattering reflector, however, it is difficult to provide a uniform cell gap with accuracy in a specified range since the scattering reflector has a projecting and depressed configuration.
If a switching element 216 such as a thin-film transistor (hereinafter referred to as TFT) or a thin-film diode (hereinafter referred to as TFD) is provided on the conventional scattering reflector, it is required to provide an electric connection between the pixel electrode 215 and the switching element 216, so that a contact hole 217 is formed (FIG. 36E). In accordance with the following conventional method, however, the contact hole 217 may be clogged or have an aperture area smaller than required and intended during the formation thereof. That is, as shown in FIGS. 36A to 36C, the contact hole 217 is formed simultaneously with the formation of the projecting portions 212a and 212b. However, there are cases where the contact hole 217 has a smaller opening or is clogged due to thermal deformation during a heat treatment performed in the process of forming the projecting portions 212a and 212b, as shown in FIG. 36D. This increases contact resistance between the pixel electrode 215 and the switching element 216 and causes a serious problem such as the degradation of the display quality of the reflective liquid crystal display device comprising the reflector.
The present invention has been achieved in view of the foregoing problems and it is therefore a first object of the present invention to provide a reflector having superior reflecting properties such as a contrast property and a paper-white property, a fabrication method therefor, and a reflective liquid crystal display device comprising the reflector.
A second object of the present invention is to provide a reflector having superior reflecting properties, a fabrication method therefor, and a reflective liquid crystal display device comprising the reflector wherein a uniform cell gap is provided.
A third object of the present invention is to provide a method of fabricating a reflector wherein a contact hole for providing an electrical connection between a pixel electrode and a switching element has a sufficiently large opening irrespective of the provision of the reflector.
The present invention may be broadly subdivided into first and second groups based on closely related aspects thereof In the first group of the invention, a description will be given to a reflector comprising a plurality of projecting and depressed structures each having projecting and depressed portions and serving as a basic unit. In the second group of the invention, a description will be given to a reflector having projecting and depressed portions covered with a metal film and a support portion serving as a spacer, which are formed integrally.
To solve the foregoing problems, a reflector in the first group of the present invention comprises: a substrate provided with a plurality of projecting and depressed structures each having a plurality of projecting and depressed portions and serving as a basic unit: and a light reflective thin film provided over the projecting and depressed structures.
The light reflecting thin film is provided over the projecting and depressed structures so that the surface configuration of the light reflecting thin films is conformal to the configuration of the projecting and depressed structures. Since each of the projecting and depressed structures has the plurality of projecting and depressed portions, the plan and cross-sectional configurations of the projecting and depressed structure can be controlled easily by varying, e.g., the distribution of the projecting and depressed portions. This allows light incident from an arbitrary direction to be reflected and scattered in the forward direction of the reflector or the like, not in the regular reflection direction.
In the foregoing arrangement, the projecting and depressed structures provided on the substrate may be arranged randomly and dispersively in an arbitrary direction.
In the arrangement, the projecting and depressed structures as the basic units are not observed repetitively with a given period so that light interference is suppressed and a phenomenon of, e.g., colored reflected light is suppressed.
In the foregoing arrangement, the projecting portions of the projecting and depressed structures may have top portions at different heights and the depressed portions of the projecting and depressed structures have bottom portions at different depths.
This allows the light reflecting thin film provided over the projecting and depressed structures to be formed with an inclined surface. By increasing or reducing a level difference between the adjacent top portions or the adjacent bottom portions, the angle formed between the inclined surface and the substrate surface (hereinafter referred to as a slope angle) can be adjusted larger or smaller. As a result, the surface of the light reflecting thin film is capable of scattering and reflecting light in directions within an anisotropic range and light can be reflected brightly in directions in a given angular range, not in the regular reflection direction. If three or more top portions are provided in the projecting and depressed structure, the top portions have different heights so that the slope angle distribution is controlled and an asymmetric cross-sectional configuration is provided. If the three or more top portions are arranged such that the heights thereof become progressively higher and that different level differences are provided between the adjacent top portions, a distribution of slope angles is produced. By varying the level difference, a desired slope angle distribution is obtained. If the three or more top portions are arranged discontinuously such that the heights thereof become progressively higher, reach a peak somewhere, and become progressively lower, the projecting and depressed structure has an asymmetric cross-sectional configuration.
In the foregoing arrangement, the projecting and depressed structures may be groups of columnar portions each composed of a plurality of minute columnar portions having different heights, the columnar portions being separate from each other or at least partially connected to each other.
In the arrangement, the plurality of minute columnar portions are formed to have different heights arranged in a specified distribution such that the slope angle distribution of the light reflecting thin film provided over the groups of columnar portions is controlled precisely. This provides a reflector having reflecting properties including a superior paper-white property.
In the foregoing arrangement, the projecting and depressed structures are staircase structures each having a plurality of stepped portions.
In the arrangement, each of the projecting and depressed structures is formed as the staircase structure having the stepped portions at different heights such that the slope angle distribution is controlled precisely. This provides a reflector having reflecting properties including a superior paper-white property.
In the foregoing arrangement, a height distribution of each of the projecting and depressed structures has a peak at a position deviated in a specified direction from a center portion of the structure and tends to decrease with distance from the peak toward a periphery thereof and the light reflecting thin film covering the projecting and depressed structures has a curved surface having a curvature larger in the specified direction than in a direction opposite to the specified direction.
In the foregoing arrangement, at least one polymer resin layer is provided between the projecting and depressed structures and the light reflecting thin film.
In the arrangement, even if the clearance between the adjacent projecting and depressed structures is large, a flat portion parallel to the substrate surface can be formed to have a gently curved configuration. Consequently, a flat region parallel to the substrate is not formed so that light reflected in the regular reflection direction is reduced. If each of the projecting and depressed structures is a group of columnar portions and a deep valley portion is formed between the adjacent columnar portions, the polymer resin layer is buried in the valley portion so that a gently curved configuration with a continuously changing height distribution is provided. If each of the projecting and depressed structures is a staircase structure, a gently curved configuration with a continuously changing height distribution can be provided such that the stepped configuration is not reflected in the surface configuration of the light reflecting thin film.
In the foregoing arrangement, the reflector may be a grating reflector for reflecting and diffracting light, the grating reflector having the plurality of projecting and depressed structures provided periodically on the substrate.
In the foregoing arrangement, each of the projecting and depressed structures in plan view has a size in the range of 1 xcexcm to 100 xcexcm.
To solve the foregoing problems, a reflector according to the present invention comprises: a substrate provided with a nonlinear element; a photosensitive resin layer provided on the substrate, the photosensitive resin layer having projecting and depressed structures in specified regions; and a pixel electrode with a light reflecting property provided on the photosensitive resin layer, the pixel electrode being electrically connected to the nonlinear element via a contact hole formed in the photosensitive resin layer, wherein a light reflecting film is provided on a bottom portion of the contact hole.
In the arrangement, the light reflecting thin film is provided at the position at which the contact hole is to be formed so that light is reflected by the vicinity of the light reflecting film during exposure. This achieves a higher exposure dose at the position at which the contact hole is to be formed than in the other exposed region. As a result, a contact hole having a generally trapezoidal cross section is formed by development so that, even if a thermal deformation is caused by, e.g., a heat treatment step, the bottom portion of the contact hole is prevented from being clogged. This implements a reflector in which an increase in contact resistance and faulty operation are suppressed.
In the foregoing arrangement, a degree of crosslinking in the photosensitive resin layer is higher in a surrounding portion of an inner wall surface of the contact hole than in the other portion thereof.
In the arrangement, irradiation of a surrounding portion of the inner wall surface of the contact hole with, e.g., UV light at a shorter wavelength or an electron beam at a shorter wavelength advances cross-linking in the irradiated region, so that it is cured. As a result, a thermal deformation resulting from a heat treatment can be prevented more positively.
To solve the foregoing problems, a reflector according to the present invention comprises: a substrate provided with a nonlinear element; a photosensitive resin layer provided on the substrate, the photosensitive resin layer having projecting and depressed structures in specified regions; and a pixel electrode with a light reflecting property provided on the photosensitive resin layer, the pixel electrode being electrically connected to the nonlinear element via a contact hole formed in the photosensitive resin layer, wherein a thin film having a surface energy higher than that of the photosensitive resin layer is provided on a bottom portion of the contact hole.
In the arrangement, the frame-shaped thin film having the surface energy higher than that of the photosensitive resin layer is provided at the position at which the contact hole is to be formed. Even if a thermal deformation is caused by, e.g., a heat treatment step, the photosensitive resin layer is prevented from flowing and clogging the bottom portion of the contact hole. This implements a reflector in which an increase in contact resistance and faulty operation are suppressed.
To solve the foregoing problems, a reflector according to the present invention comprises: a substrate provided with a nonlinear element, a photosensitive resin layer provided on the substrate, the photosensitive resin layer having projecting and depressed structures in specified regions; and a pixel electrode with a light reflecting property provided on the photosensitive resin layer, the pixel electrode being electrically connected to the nonlinear element via a contact hole formed in the photosensitive resin layer, wherein the contact hole is provided such that a degree of crosslinking is higher in a surrounding portion of an inner wall surface of the contact hole than in the other portion thereof.
In the arrangement, irradiation of surrounding portion of the inner wall surface of the contact hole with, e.g., UV light at a shorter wavelength or an electron beam at a shorter wavelength advances cross-linking in the irradiated region. As a result, a thermal deformation resulting from a heat treatment can be prevented more positively.
To solve the foregoing problems, a reflective display device according to the present invention comprises: a counter substrate with transparency; a reflector disposed in opposing relation to the counter substrate, the reflector including a substrate provided with a plurality of projecting and depressed structures each having a plurality of projecting and depressed portions and serving as a basic unit and a light reflecting thin film provided over the projecting and depressed structures; and a liquid crystal layer held between the counter substrate and the reflector.
The arrangement provides a reflective liquid crystal display device comprising a reflector having a superior contrast property and a superior paper-white property.
To solve the foregoing problems, a method of fabricating a reflector according to the present invention comprises. a step of forming a photosensitive resin layer on a substrate; an exposing step of irradiating the photosensitive resin layer with light via a photomask having light shielding portions patterned into specified configurations; a developing step of developing the photosensitive resin layer irradiated with the light to form a plurality of resist columns; a heat treatment step of performing a heat treatment with respect to the substrate formed with the plurality of resist columns and thereby forming groups of columnar portions each composed of a plurality of minute columnar portions having different heights, the columnar portions being separate from each other or at least partially connected to each other; and a step of forming a light reflecting thin film over the groups of columnar portions, wherein, as the photomask, a mask formed with a plurality of unit components each composed of a plurality of minute shielding portions having different heights is used.
In accordance with the method, the photosensitive resin layer formed on the substrate is initially exposed and then developed to form the resist columns having heights in a uniform distribution. The resist columns are then thermally deformed by performing the heat treatment with respect to the substrate formed with the resist columns, thereby forming the plurality of minute columns having different heights. The columnar portions have different heights because the resist columns have different plan configurations prior to the heat treatment step in response to the configurations and sizes of the light shielding portions. If a photosensitive resin material in which the area occupied by the plan configuration of the resist column and the height of the resist column thermally deformed (i.e., the height of the columnar portion) satisfy a linearly functional relationship is used and the processing temperature is set within a specified range, the resist column occupying a larger area can form a higher columnar portion. By varying the area, therefore, the columnar portion can be formed to have a controlled height so that a reflector is produced in which the light reflecting thin film provided over the group of columnar portions has a precisely controlled slope angle distribution.
To solve the foregoing problems, a method of fabricating a reflector according to the present invention comprises: a step of forming a photosensitive resin layer on a substrate; an exposing step of irradiating the photosensitive resin layer with light via a photomask having light shielding portions each having a progressively varying light shielding rate; a developing step of developing the photosensitive resin layer irradiated with the light to form a plurality of staircase resist columns; a heat treatment step of performing a heat treatment with respect to the substrate formed with the plurality of staircase resist columns to round off respective angular edges of the resist columns and thereby forming staircase structures each having a plurality of stepped portions; and a step of forming a light reflecting thin film over the staircase structures.
In accordance with the method, the photosensitive resin layer is irradiated with light based on the light shielding rates of the light shielding portions of the photomask. Accordingly, optical decomposition and cross-linking proceed to different degrees in different regions so that resist columns each having a staircase cross-sectional configuration are formed after the development step. By further performing the heat treatment step, the staircase structures each having the plurality of stepped portions can be formed. By thus varying the light shielding rate in the photomask, the staircase structures having the stepped portions at controlled heights are formed so that the light reflecting thin film provided over the staircase structures has a precisely controlled slope angle distribution.
To solve the foregoing problems, a method of fabricating a reflector according to the present invention comprises: a step of forming a photosensitive resin layer on a substrate; a step of preparing a plurality of photomasks each having light shielding portions patterned into specified configurations, each of the light shielding portions of the different photomasks covering a light shielding range which is different in size from one photomask to another, each of the light shielding portions of any of the photomasks covering a larger shielding range and each of the light shielding portions of the photomask covering a next smaller shielding range having a relationship therebetween such that the next smaller light shielding range is included in the larger light shielding range; an exposing step of irradiating the photosensitive resin layer with light by successively using the photomasks in the order of decreasing size of the light shielding range of the shielding portion; a developing step of developing the photosensitive resin layer irradiated with the light to form a plurality of staircase resist columns; a heat treatment step of performing a heat treatment with respect to the substrate formed with the staircase resist columns to round off respective angular edges of the resist columns and thereby forming staircase structures each having a plurality of stepped portions; and forming a light reflecting thin film over the staircase structures.
In accordance with the method, the cumulative exposure dose is controlled for each of the regions by performing at least two or more exposing steps and using the photomask covering a light shielding range which decreases as the exposing steps are performed one after another. As a result, optical decomposition and cross-linking proceed to different degrees from one region to another so that the staircase resist columns are formed by the developing step. This allows formation of the staircase structures each having the plurality of stepped portions.
To solve the foregoing problems, a method of fabricating a reflector according to the present invention is a method of fabricating a reflector having a substrate provided with a nonlinear element, a photosensitive resin layer provided on the substrate and having projecting and depressed structures in specified regions, and a pixel electrode with a light reflecting property provided on the photosensitive resin layer, the pixel electrode being electrically connected to the nonlinear element via a contact hole formed in the photosensitive resin layer, the method comprising: a step of forming the nonlinear element on the substrate; a light-reflecting-film forming step of forming, at a position at which the contact hole is to be formed, a light reflecting film patterned into a specified configuration; a coating step of coating a photosensitive resin material over the substrate and the light reflecting film; an exposing step of irradiating the photosensitive resin material with light via a photomask having light shielding portions patterned into specified configurations; a developing step of developing the photosensitive resin material irradiated with the light to form the photosensitive resin layer comprising the contact hole and a plurality of resist columns formed in specified regions; a heat treatment step of performing a heat treatment with respect to the photosensitive resin layer and thereby thermally deforming and rounding off respective edge portions of the plurality of resist columns; a post-baking step of performing a heat treatment with respect to the photosensitive resin layer and thereby curing the photosensitive resin layer; and a pixel-electrode forming step of forming the pixel electrode with the light reflecting property on the photosensitive resin layer.
In accordance with the method, the light reflecting film is formed preliminarily at the position at which the contact hole is to be formed so that light is reflected by the vicinity of the light reflecting film when light is radiated in the exposing step. Accordingly, the exposure dose in the vicinity of the light reflecting film is higher than in the other region. In addition, the developing step allows formation of the contact hole having a generally trapezoidal cross section. The configuration and size of the opening portion of the contact hole nearly correspond to the pattern configuration of the photomask and become larger with approach toward the bottom portion thereof.
Subsequently, the heat treatment is performed with respect to the plurality of resist columns each formed in the specified region to deform the respective edge portions thereof. Although the opening portion and inner wall surface of the contact hole are thermally deformed, there can be formed a contact hole having an unclogged bottom portion because of the trapezoidal cross-sectional configuration. This allows formation of a reflector in which an increase in contact resistance and faulty operation are suppressed.
To solve the foregoing problems, a method of fabricating a reflector according to the present invention is a method of fabricating a reflector having a substrate provided with a nonlinear element, a photosensitive resin layer provided on the substrate and having projecting and depressed structures in specified regions, and a pixel electrode with a light reflecting property provided on the photosensitive resin layer, the pixel electrode being electrically connected to the nonlinear element via a contact hole formed in the photosensitive resin layer, the method comprising: a step of forming the nonlinear element on the substrate; a thin-film forming step of forming, at a position at which the contact hole is to be formed, a frame-shaped thin film having a surface energy higher than that of the photosensitive resin layer; a coating step of coating a photosensitive resin material over the substrate and the thin film; an exposing step of irradiating the photosensitive resin material with light via a photomask having light shielding portions patterned into specified configurations; a developing step of developing the photosensitive resin material irradiated with the light to form the photosensitive resin layer comprising the contact hole and a plurality of resist columns formed in specified regions; a heat treatment step of performing a heat treatment with respect to the photosensitive resin layer and thereby thermally deforming and rounding off respective edge portions of the plurality of resist columns; a post-baking step of performing a heat treatment with respect to the photosensitive resin layer and thereby curing the photosensitive resin layer; and a pixel-electrode forming step of forming the pixel electrode with the light reflecting property on the photosensitive resin layer.
In accordance with the method, the thin film having the surface energy higher than that of the photosensitive resin layer has been formed preliminarily at the position at which the contact hole is to be formed. Even if the opening portion and inner wall surface of the contact hole are thermally deformed, they are prevented from flowing as a result of the thermal deformation. This prevents the bottom portion of the contact hole from being clogged and allows formation of a reflector in which an increase in contact resistance and faulty operation are suppressed. The thin film has been formed into a frame-shaped configuration to provide an electric connection between the switching element and the pixel electrode.
To solve the foregoing problems, a method of fabricating a reflector according to the present invention is a method of fabricating a reflector having a substrate provided with a nonlinear element, a photosensitive resin layer provided on the substrate and having projecting and depressed structures in specified regions, and a pixel electrode with a light reflecting property provided on the photosensitive resin layer, the pixel electrode being electrically connected to the nonlinear element via a contact hole formed in the photosensitive resin layer, the method comprising: a step of forming the nonlinear element on the substrate; a thin-film forming step of forming, on a drain electrode of the nonlinear element, a thin film having a surface energy higher than that of the photosensitive resin layer; a coating step of coating a photosensitive resin material over the substrate and the thin film; an exposing step of irradiating the photosensitive resin material with light via a photomask having light shielding portions patterned into specified configurations; a developing step of developing the photosensitive resin material irradiated with the light to form the photosensitive resin layer comprising the contact hole and a plurality of resist columns formed in specified regions; a heat treatment step of performing a heat treatment with respect to the photosensitive resin layer and thereby thermally deforming and rounding off respective edge portions of the plurality of resist columns; a removing step of removing the thin film by ashing; a post-baking step of performing a heat treatment with respect to the photosensitive resin layer and thereby curing the photosensitive resin layer; and a pixel-electrode forming step of forming the pixel electrode with the light reflecting property on the photosensitive resin layer.
In accordance with the method, even if the thin film which is not frame-shaped is formed, an electric connection is provided between the nonlinear element and the pixel electrode and the bottom portion of the contact hole is prevented from being clogged if the thin film is removed by ashing. This allows formation of a reflector in which an increase in contact resistance and faulty operation are suppressed.
To solve the foregoing problems, a method of fabricating a reflector according to the present invention is a method of fabricating a reflector having a substrate provided with a nonlinear element, a photosensitive resin layer provided on the substrate and having projecting and depressed structures in specified regions, and a pixel electrode with a light reflecting property provided on the photosensitive resin layer, the pixel electrode being electrically connected to the nonlinear element via a contact hole formed in the photosensitive resin layer, the method comprising: a step of forming the nonlinear element on the substrate; a coating step of coating a photosensitive resin material on the substrate; an exposing step of irradiating the photosensitive resin material with light via a photomask having light shielding portions patterned into specified configurations; a developing step of developing the photosensitive resin material irradiated with the light to form the photosensitive resin layer comprising the contact hole and a plurality of resist columns formed in specified regions; a light irradiating step of irradiating a surrounding portion of the contact hole with light at a shorter wavelength; a heat treatment step of performing a heat treatment with respect to the photosensitive resin layer and thereby thermally deforming and rounding off respective edge portions of the plurality of resist columns; a post-baking step of performing a heat treatment with respect to the photosensitive resin layer; and a pixel-electrode forming step of forming the pixel electrode with the light reflecting property on the photosensitive resin layer, wherein a degree of crosslinking is higher in a surrounding portion of an inner wall surface of the contact hole.
In accordance with the method, irradiation of a surrounding portion of the contact hole that has been formed by the exposing and developing steps with light at a shorter wavelength advances cross-linking in the opening portion and inner wall surface of the contact hole, so that curing proceeds to a higher degree than in the other portion. Even if the heat treatment step is performed, therefore, the surrounding portion of the contact hole is inhibited from being thermally deformed. This prevents the bottom portion of the contact hole from being clogged and allows formation of a reflector in which an increase in contact resistance and faulty operation are suppressed.
The foregoing arrangement further comprises, after the heat treatment step, a light irradiating step of irradiating the surrounding portion of the contact hole with light at a shorter wavelength.
By thus performing again the light irradiating step after the heat treatment step, thermal deformation during the post-baking step is suppressed and an increase in contact resistance and faulty operation are further suppressed.
To solve the foregoing problems, a method of fabricating a reflector comprises: a step of forming a photosensitive resin layer on a substrate; an exposing step of irradiating the photosensitive resin layer with light via a first photomask having light shielding portions patterned into specified configurations; a developing step of developing the photosensitive resin layer irradiated with the light to form a plurality of resist columns; an irradiating step of irradiating respective specified regions of the plurality of resist columns with light at a shorter wavelength via a second photomask having openings patterned into specified configurations; a heat treatment step of performing a heat treatment with respect to the resist columns and thereby thermally deforming respective edge portions of the plurality of resist columns to form projecting and depressed structures each having an asymmetrical cross-sectional configuration; a post-baking step of performing a heat treatment with respect to the photosensitive resin layer; and a pixel-electrode forming step of forming a pixel electrode with a light reflecting property on the photosensitive resin layer.
In accordance with the method, irradiation of the respective specified regions of the resist columns that have been formed by performing the exposing and developing steps with the Light at a shorter wavelength advances cross-linking in the irradiated regions, so that curing proceeds to a higher degree than in the other portion. As a result, unirradiated regions undergo significant thermal deformation, while the cured portions undergo a lower degree of thermal deformation. This allows formation of the projecting and depressed structures each having an asymmetric cross-sectional configuration and fabrication of a reflector capable of scattering and reflecting light in directions within an anisotropic range. If conditions for irradiation in the light irradiating step are determined properly, the projecting and depressed structures each having the asymmetric cross-sectional configuration and a desired slope angle can be formed with ease and controllability.
The foregoing arrangement further comprises, after the heat treatment step, a light irradiating step of irradiating the plurality of projecting and depressed structures with light at a shorter wavelength.
By thus performing again the light irradiating step after the heat treatment step, the projecting and depressed structures each having an asymmetric cross-sectional configuration are prevented from being thermally deformed in the post-baking step and there can be fabricated a reflector having desired reflecting properties.
To solve the foregoing problems, a reflective display device according to the present invention is a reflective display device having a liquid crystal layer provided between a pair of substrates, wherein one of the pair of substrates is provided with projecting and depressed portions covered with a metal film and with a support portion for supporting the other of the pair of substrates, the projecting and depressed portions and the support portion being molded integrally.
In the case where one of the substrates is provided with the projecting and depressed portions, as in the foregoing arrangement, if spacers are scattered to provide a specified cell gap between the pair of substrates, the cell gap therebetween becomes nonuniform over a surface of the substrate so that uneven display is recognized visually. However, if the projecting and depressed portions and the support portion for supporting the other of the substrates are formed integrally, there is no need to scatter the spacers and a uniform cell gap is provided. This reduces the occurrence of uneven display and provides a high display quality.
In the foregoing arrangement, the projecting and depressed portions may be pyramidal or conical.
In the foregoing arrangement, if an angle formed between an inclined surface of the pyramidal projecting and depressed portions and a horizontal surface or an angle formed between a generating line of the conical projecting and depressed portions and a horizontal surface is assumed to be a slope angle, the projecting and depressed portions may be dispersively arranged at different slope angles and the slope angles are in the range of 4xc2x0 to 16xc2x0.
The foregoing arrangement may further comprises a polymer resin layer molded integrally with the projecting and depressed portions and with the support portion for supporting the other of the substrates, the polymer resin layer being provided on one of the substrates.
In the foregoing arrangement, a plurality of nonlinear elements may be provided on one of the substrates and a contact hole for providing an electric connection between the nonlinear elements and the metal film is provided in the polymer resin layer.
In the foregoing arrangement, a resin film molded integrally with the projecting and depressed portions and with the support portion for supporting the other of the substrates may be laminated on one of the substrates.
In the foregoing arrangement, the resin film may be made of a photosensitive resin.
In the foregoing arrangement, one of the substrates may be a plastic substrate molded with the projecting and depressed portions and with the support portion for supporting the other of the substrates.
To solve the foregoing problems, a reflective display device according to the present invention is a reflective display device having a photosensitive resin layer provided on a substrate and a metal film provided on the photosensitive resin layer, wherein the photosensitive resin layer is formed by exposing, to light, a photosensitive resin coated on the substrate via a photomask and developing the exposed photosensitive resin, the photosensitive resin layer having a projecting and depressed surface formed by exposing the photosensitive resin to the light via the photomask having a light shielding pattern composed of groups of minute halftone dots smaller than a resolution limit of an exposing device used for the exposure and a resolution limit of the photosensitive resin, a mean light transmittance of the light shielding pattern being nonuniform over a surface of the photomask.
In the foregoing arrangements, the projecting and depressed portions are formed in the photosensitive resin layer by using the photomask having the light shielding pattern capable of half-tone representation which cannot be implemented with a conventional chromium mask or the like and finely controlling the configuration of the projecting and depressed portions. This permits light incident from an arbitrary direction to be scattered and reflected in the forward direction of the reflective display device or the like, not in the regular reflection direction, and enables bright image display with excellent whiteness.
To solve the foregoing problems, a method of fabricating a reflective display device according to the present invention is a method of fabricating a reflective display device comprising a light modulating layer between a pair of substrates, the method comprising the steps of forming a polymer resin layer on one of the pair of substrates; pressing a platen provided with a projecting and depressed pattern composed of a group of minute projecting and depressed patterns and a hole against the polymer resin layer; curing the polymer resin layer and mold releasing the platen from the polymer resin layer; forming a metal film on the polymer resin layer; and thereby shaping the polymer resin layer into the projecting and depressed pattern to integrally mold minute projecting and depressed portions in a surface of the polymer resin layer with a support portion for supporting the other of the pair of substrates.
In the conventional reflector, the projecting and depressed configurations have been formed by forming the projecting portions by using a photoresist, heat-melting the projecting portions, and thereby rounding off the respective angular edges thereof. Therefore, it has been difficult to control the curved configurations of the projecting and depressed portions. However, the foregoing method allows formation of the projecting and depressed portions having precisely controlled curved configurations in the polymer resin layer because it performs shaping by using the platen provided with the projecting and depressed pattern composed of the group of minute projecting and depressed patterns and the hole. This reduces reflection in the regular reflection direction and allows fabrication of a reflective display device with excellent brightness and whiteness. Moreover, since the projecting and depressed portions and the support portion for supporting the counter substrate are formed integrally, there is no need to scatter spacers and a uniform cell gap is provided. This reduces the occurrence of uneven display and provides a reflective display device with a high display quality.
In the foregoing method, if the polymer resin layer formed on one of the substrates is a photosensitive resin layer, a platen with transparency is used as the platen and the polymer resin layer may be cured by irradiating the photosensitive resin layer with light via the platen.
In the foregoing method, if the polymer resin layer formed on one of the substrates is a thermoplastic resin layer, the platen may be pressed against the thermoplastic resin layer with the application of heat.
In the foregoing method, a nonlinear element is provided on one of the substrates and a platen having a projecting portion for forming a contact hole at a position corresponding to an output terminal portion of the nonlinear element may be used as the platen.
In the foregoing method, a bottom portion of the contact hole in the polymer resin layer may be etched immediately after the platen is mold released from the polymer resin layer till the output terminal portion of the nonlinear element is exposed. This satisfactorily exposes the output terminal portion of the nonlinear element even if the contact hole to be formed by shaping has an insufficient opening area and suppresses an increase in contact resistance. As a result, there can be fabricated a reflective display device with a particularly high display quality in a motion picture display.
To solve the foregoing problems, a method of fabricating a reflective display device according to the present invention is a method of fabricating a reflective display device comprising a light modulating layer between a pair of substrates, the method comprising the steps of: pressing a platen provided with a projecting and depressed pattern composed of a group of minute projecting and depressed patterns and a hole against one of the pair of substrates; curing one of the substrates and mold releasing the platen from one of the substrates; forming a metal film on one of the substrates; and thereby shaping one of the substrates into the projecting and depressed pattern to integrally mold minute projecting and depressed portions in a surface of one of the substrates with a support portion for supporting the other of the substrates.
In the fabrication of a substrate, the step of pressing a platen with satisfactory flatness against the substrate has been performed conventionally to smooth the surface thereof. The foregoing method achieves a reduction in the number of process steps and lower cost by shaping the substrate into the projecting and depressed pattern with the use of the platen provided with the projecting and depressed pattern and smoothing the substrate.
In the foregoing method, if one of the substrates is made of a photosensitive resin, a platen with transparency is used as the platen and one of the substrates may be cured by irradiating one of the substrates with light via the platen.
In the foregoing method, if one of the substrates is made of a thermoplastic resin, the platen may be pressed against one of the substrates with the application of heat.
To solve the foregoing problems, a method of fabricating a reflective display device according to the present invention is a method of fabricating a reflective display device comprising a light modulating layer between a pair of substrates, the method comprising the steps of: forming a polymer resin layer over a mold provided with a projecting and depressed pattern composed of a group of minute projecting and depressed patterns; bonding the mold to one of the pair of the substrates such that the polymer resin layer faces the substrate and releasing the mold from the polymer resin layer to laminate the polymer resin layer on one of the substrates; forming a metal film over the polymer resin layer; and thereby shaping the polymer resin layer into the projecting and depressed pattern to form minute projecting and depressed portions in a surface of the polymer resin layer.
If a polymer resin is coated on the substrate and the polymer resin is shaped into the projecting and depressed pattern by using the platen, e.g., the substrate may be damaged in pressing the platen against the substrate. However, if the polymer resin layer that has been shaped into the projecting and depressed pattern by using the platen provided with the projecting and depressed pattern is prepared in advance and formed on the substrate, the substrate will not be broken. This allows fabrication of a reflective display device with an improved production yield. The foregoing method also achieves a reduction in fabrication cost since the process of forming the polymer resin layer over the platen can be performed in a shorter time than the process of shaping the polymer resin formed on the substrate by pressing the platen thereagainst.
In the foregoing method, a base film made of a polymer resin may be used as the mold.
In the foregoing method, a mold having, at a specified position, a hole for forming a support portion for supporting the other of the pair of substrates may be used as the mold.
To solve the foregoing problems, a method of fabricating a reflector comprises the steps of: coating a photosensitive resin layer on a substrate; exposing the photosensitive resin layer to light via a photomask; developing the exposed photosensitive resin layer to form projecting and depressed portions in the photosensitive resin layer; and forming a reflective film over the projecting and depressed surface, wherein the photomask has a light shielding pattern composed of groups of minute half-tone dots smaller than a resolution limit of an exposing device used in the exposing step and a resolution limit of the photosensitive resin layer and a mean light transmittance of the light shielding pattern is nonuniform over a surface of the photomask.
Since the foregoing method uses the photomask having the light shielding pattern composed of the groups of minute halftone dots smaller than the resolution limit of the exposing device and the resolution limit of the photosensitive resin layer, it can implement halftone representation that has been impossible with a conventional photomask and the ability to represent details is improved remarkably. As a consequence, the projecting and depressed portions having, e.g., a gently inclined surface can be formed and fine control of the configurations of the projecting and depressed portions can be effected properly. Since a normal exposing device or the like can be used, there is no need to introduce new equipment.
Since the light shielding pattern has a nonuniform mean transmittance over a surface of the photomask, projecting and depressed portions having different heights and depth can be formed in a variety.
In the foregoing method, a nonlinear element is provided on the substrate and a mask having a light shielding portion or a light non-shielding portion provided at a portion corresponding to an output portion of the non-linear element may be used as the photomask.
The method allows formation of a contact hole in the portion of the photosensitive resin layer corresponding to the output portion of the nonlinear element. If the photomask is provided with the light shielding portion, a photosensitive resin layer composed of a negative resist can be used as the photosensitive resin layer. If the photomask is provided with a light non-shielding portion, a photosensitive resin layer composed of a positive resist can be used as the photosensitive resin layer.